1 The momentum is with Chelsea …

Manchester United are not a team on the slide. Their return over the last nine league games is 16 points which, while not staggering, remains respectable. Their displays in the Champions League, with the victories over Chelsea and Schalke, within that sequence certainly caught the eye. And yet they are steadily being caught as the London side generate rhythm to match their breathless start to the campaign.

Chelsea's return in the same period is 25 points, starting with the victory against United at Stamford Bridge. At half-time that evening, when they trailed to Wayne Rooney's goal, the reigning champions were facing an 18-point deficit from the leaders. Win at Old Trafford on Sunday and they will be top. The momentum has been whipped up late, the rat-a-tat of victories initially masked by European commitments but, after a slight stumble at Stoke, reinvigorated with five wins in succession. They remain the division's stingiest defence while players absent, injured or ill, in the winter are revived, imposing themselves again.

This is the kind of run that United are more used to generating, the type to chase down Newcastle in the mid-1990s or to prove Arsenal were no longer Invincibles. It is also the kind that secured Carlo Ancelotti's side their title last season, when United were one of the sides beaten in an eight-game sequence that brought 21 points and 33 goals. The manager joked at the weekend that his team are happiest when the temperature is warmer. They are unrecognisable from the shambles that secured only 10 points from 11 games as winter set in.

2 … but United's home form still makes them favourites

If United need reminding that the title remains theirs to lose, then a glance at their home record this season should provide the fillip. Sir Alex Ferguson's side have not lost at Old Trafford since Chelsea prevailed there 13 months ago and, of the 17 clubs to have visited this season, only West Bromwich Albion have left with a point. That is the form that has sustained United's challenge given a paltry five wins on their travels. If they go on to claim the title, they will do so having achieved the fewest number of away victories since Liverpool needed only five in 1976-77.

They will take heart from the Champions League victory achieved at Old Trafford last month and that all five of the league meetings between the division's top three have been won by the home side this season, an indication again that Chelsea's task is onerous. "United are still favourites because, when you play at home for the title, you have an advantage," said Arsène Wenger. "I believe United, every year they win the title, they win it at Old Trafford. You compare the record of United and Arsenal away from home and you see that we are always really comparable. They get the points at Old Trafford." They have done just that this season and, if they end the campaign unbeaten at home, they will surely be crowned champions.

3 Time for Fernando Torres to return to the bench?

Ancelotti appeared to take an unnecessary risk by trying to reintegrate Fernando Torres from the start on Saturday. A first goal for his new club and a week of training had apparently convinced the manager to play the £50m Spaniard in alongside Didier Drogba for the first time in six games, despite the fact that the combination has always previously felt so awkward. There was no quibbling with Torres's movement or commitment yet again but the system still seemed disjointed.

The striker had been selected instead of Drogba at Old Trafford in the Champions League but was so ineffective that he was withdrawn at the break. But, even with time to prepare, it seems inconceivable that the champions will not return to their more conventional 4-3-3 with the Ivorian barging through the centre of the front trident, flanked by the energetic Malouda and Salomon Kalou for the season's defining fixture. They had revelled in the familiarity of the return to the comfortable shape of last year in recent weeks, the midfield even benefiting from Mikel John Obi's presence at its base. That gives Lampard and Michael Essien, or Ramires, scope to be more adventurous. Smoothing Torres's passage into the team remains the long-term objective but at present Ancelotti is concerned only about the short term. The Spaniard may have to wait.

4 United must address their midfield conundrum

Ferguson's side need only avoid defeat on Sunday to maintain their advantage going into the last two fixtures, with logic suggesting he will return to the system and personnel who beat Chelsea home and away in their Champions League quarter-final. That would see Anderson, disappointing at Arsenal on Sunday and still an erratic and inconsistent performer, dropping out of the starting line-up to be replaced, most likely, by Ryan Giggs. The veteran could sit deep alongside Michael Carrick – impressive in the European ties – with Park Ji-sung and one of either Nani or Antonio Valencia offering width. Wayne Rooney, upon whom so much depends, could drop back if required to ensure the home side are not outnumbered in the centre, leaving Javier Hernández to explore the channels.

United should not be fatigued by any midweek European exertions. Schalke were swept aside so easily in Gelsenkirchen last week that the semi-final appears settled with Ferguson intent on resting personnel with Sunday's match in mind. Paul Scholes, Dimitar Berbatov and Michael Owen may all start on Wednesday night, offering the likes of Rooney, Hernández and Giggs time to recharge batteries. This should be a collision between these sides' strongest selections.

5 Can Chelsea combat Hernández and Rooney?

Chelsea will include one player who could not feature in the Champions League tie. They should be more confident at their ability to nullify the Hernández/Rooney partnership given David Luiz's availability. The Brazilian has settled in smoothly to life in the Premier League – Chelsea have yet to lose a game in which he has started – and, while there has been the odd flash of ill discipline in terms of his instinct to maraud up-field, and his eagerness to dive into a tackle, his involvement strengthens them as a unit.

Branislav Ivanovic, who played in the centre in the European games, is a more reliable right-back than either Paulo Ferreira or José Bosingwa and has already struck up a partnership with David Luiz. On Saturday against Tottenham the pair switched whenever Gareth Bale veered infield, each covering the other's duties. That bodes well, given Hernández's ability to drag centre-backs out of position and create space for Rooney to exploit. There was uncharacteristic defensive vulnerability to Ancelotti's side in both the Champions League games, for which David Luiz was ineligible. This time the man who scored the equaliser at Stamford Bridge in March will be hoping to make an impact once again.